Electronic circuit structure and method for forming same

ABSTRACT

A thin film transistor (TFT) structure is implemented. This embodiment is much less sensitive than conventional TFTs to alignment errors and substrate distortion. In such a configuration, there is no need to define gate features, so the layout is simplified. Moreover, the gate layer may be patterned by several inexpensive printing or non-printing methods.

CROSS REFERENCE TO RELATED PATENTS AND APPLICATIONS

This application is related to U.S. application Ser. No. ______, filedon even date herewith, entitled, “Thin Film Transistors and High FillFactor Pixel Circuits and Methods for Forming Same,” and naming Danielet al. as inventors (bearing Attorney Docket No. 20061016-US-NP, XERZ 201743) and U.S. application Ser. No. ______, filed on even dateherewith, entitled, “Method and Structure for Establishing Contacts inThin Film Transistor Devices,” naming Daniel et al. as inventors(bearing Attorney Docket No. 20070345-US-NP, XERZ 2 01958).

BACKGROUND

Typically, thin film transistor or active-matrix pixel circuits requirecareful alignment of the source-drain layer(s) to the gate layer.However, aligning layers in printed (organic) electronic circuits is achallenge, particularly on flexible substrates where substratedistortion and shrinkage often occur. It is difficult to compensate forsuch deformation of the substrate. This has significance becausemisalignment can lead to a non-working transistor.

To attempt to solve the problem, wide gate features have been used toensure the source-drain region overlaps with the gate region. Thisapproach and resulting overlap, however, cause high and undesiredparasitic capacitances.

To illustrate these problems, FIGS. 1( a)-(e) show the elements of aprinted pixel array. Such an array is typically used in active-matrixbackplanes for displays, image sensors or other sensor arrays. As shown,a gate layer 10 (FIG. 1( a)), having defined gate features, and a datalayer 12 (FIG. 1( b)), with data lines and pixel pads, should be alignedso that the gate features end up underneath the channel region 14 toform a thin film transistor (TFT) 16 (FIG. 1( c)). As noted above,misalignment can lead to non-functioning TFTs (FIG. 1( d)). In thisregard, the source s and gate g overlap, however, there is no overlapbetween the gate g and the drain d. Thus, the TFT will not functionproperly. If the gate feature is chosen to be wide to compensate forpotential misalignment as alluded to above, then the excessive parasiticcapacitance due to overlapping s/g or s/d regions can cause problems(e.g. feedthrough voltage in pixels or reduced switching speed of TFTs)(FIG. 1( e)). So, solutions to these problems are desired.

Self-aligned patterning methods—using, for example, backside exposure ofphotoresist—are used in photolithographic patterning methods. However,for electronic circuits patterned using printing methods, bettersolutions are desired.

INCORPORATION BY REFERENCE

U.S. application Ser. No. ______, filed on even date herewith, entitled,“Thin Film Transistors and High Fill Factor Pixel Circuits and Methodsfor Forming Same,” and naming Daniel et al. as inventors (bearingAttorney Docket No. 20061016-US-NP, XERZ 2 01743) and U.S. applicationSer. No. ______, filed on even date herewith, entitled, “Method andStructure for Establishing Contacts in Thin Film Transistor Devices,”naming Daniel et al. as inventors (bearing Attorney Docket No.20070345-US-NP, XERZ 2 01958) are incorporated herein by reference intheir entirety.

BRIEF DESCRIPTION

In one aspect of the presently described embodiments, a thin filmtransistor device comprises a gate line patterned to extend in a firstdirection, a first dielectric layer formed over the gate line, a seconddielectric pattern deposited on the first dielectric layer and defininga transistor channel region comprising the gate line, a conductive layerformed on the second dielectric pattern and in alignment with the seconddielectric pattern, and, a semiconductor formed in the channel.

In another aspect of the presently described embodiments, the seconddielectric pattern is oriented on the first dielectric layer in adirection substantially perpendicular the gate line.

In another aspect of the presently described embodiments, the conductivelayer is in alignment with the second dielectric pattern.

In another aspect of the presently described embodiments, the device ispart of an active-matrix display backplane.

In another aspect of the presently described embodiments, the device isused in an image sensor.

In another aspect of the presently described embodiments, the firstdielectric has a low surface energy.

In another aspect of the presently described embodiments, the seconddielectric is a polymer or a composite of polymer and inorganicparticles.

In another aspect of the presently described embodiments, the seconddielectric is printed.

In another aspect of the presently described embodiments, the seconddielectric has a high surface energy.

In another aspect of the presently described embodiments, the conductivelayer is aligned on the second dielectric by fluidic pinning.

In another aspect of the presently described embodiments, the devicecomprises a pixel circuit.

In another aspect of the presently described embodiments, the devicecomprises a pixel capacitor printed over a portion of the gate line anda portion of the pixel pad.

In another aspect of the presently described embodiments, the dielectricin the region of the pixel capacitor is thin relative to a thickness ofsecond dielectric features.

In another aspect of the presently described embodiments, thesemiconductor is deposited from a solution.

In another aspect of the presently described embodiments, thesemiconductor is jet-printed.

In another aspect of the presently described embodiments, the gate lineincludes a meandering shaped edge.

In another aspect of the presently described embodiments, the device isconnected to at least one second transistor device to form at least oneof an inverter, shift register, memory cell, latch circuit or amplifiercircuit.

In another aspect of the presently described embodiments, the methodcomprises patterning a gate line on a substrate in a first direction,depositing a dielectric over the gate line, printing polymer features ina direction perpendicular to the first direction to form a channelcomprising the gate line, forming a conductive layer on the polymerfeatures, and, forming a semiconductor in the channel.

In another aspect of the presently described embodiments, the forming ofthe conductive layer comprises pinning.

In another aspect of the presently described embodiments, the methodfurther comprises a pixel capacitor to connect a gate line with aselected portion of the polymer features.

In another aspect of the presently described embodiments, anactive-matrix pixel circuit comprises an array of gate electrodes formedon a substrate, the gate electrodes shaped as substantially parallelstripes oriented in a first direction, a first dielectric layer formedover the gate electrodes, a second dielectric layer patterned on thefirst dielectric layer and defining transistor channel regionscomprising the gate line, a conductive layer formed on the seconddielectric layer and in alignment with the second dielectric pattern,and, a semiconductor formed in the channel.

In another aspect of the presently described embodiments, the seconddielectric layer comprises a phase-change polymer.

In another aspect of the presently described embodiments, anactive-matrix pixel circuit comprises an array of gate electrodes formedon a substrate, the gate electrodes shaped as substantially parallelstripes oriented in a first direction, a first dielectric layer formedover the gate electrodes, a second dielectric layer of a first thicknesspatterned on the first dielectric layer and defining transistor channelregions comprising the gate line, a third dielectric layer of a secondthickness patterned on the first dielectric layer and defining a pixelcapacitor region, a conductive layer formed on the second and thirddielectric layer and in alignment with the second and third dielectricpattern, and, a semiconductor formed in the channel.

In another aspect of the presently described embodiments, at least oneof the second dielectric layer and the third dielectric layer comprisesa phase-change polymer.

In another aspect of the presently described embodiments, anactive-matrix pixel circuit comprises an array of gate electrodes formedon a substrate, the gate electrodes having a meandering shapedseparation with a substantially constant spacing between neighboringgate electrodes, a first dielectric layer formed over the gateelectrode, a second dielectric layer patterned on the first dielectriclayer and defining transistor channel regions comprising the gate line,a conductive layer formed on the second dielectric layer and inalignment with the second dielectric pattern, and, a semiconductorformed in the channel.

In another aspect of the presently described embodiments, the seconddielectric layer comprises a phase-change polymer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1( a)-(e) illustrate a configuration identifying a problem in theprior art;

FIGS. 2( a)-(f) illustrate one of the presently described embodiments;

FIGS. 3( a)-(b) illustrate another of the presently describedembodiments;

FIG. 4 illustrates still another of the presently described embodiments;and,

FIG. 5 illustrates still another of the presently described embodiments.

DETAILED DESCRIPTION

According to the presently described embodiments, a bottom-gate thinfilm transistor (TFT) structure is implemented. This embodiment is muchless sensitive than conventional TFTs to alignment errors and substratedistortion. In such a configuration, there is no need to define narrowgate features, so the layout is simplified. Moreover, the gate layer maybe patterned by several inexpensive printing or non-printing methods.

Examples of various forms of the presently described embodiments areshown in FIGS. 2-5. Both the method of fabrication and the resultingstructure should be apparent from the following description. Further, itwill be appreciated that other forms and techniques are contemplated bythe teachings herein.

With reference to FIG. 2( a), in the formation of an active-matrix pixelcircuit, a gate layer or area is patterned to form, for example, gatelines or a gate pattern using relatively simple shapes, such as lines orstripes 100. The gate layer is patterned on a suitable substrate 98,including polymer, metal, glass, ceramic, rigid or flexible substrates.Example materials are stainless steel foil, polyester foil (Mylar),polyethylene naphthalene (PEN) foil, FR4 printed circuit board, etc.Such patterning may be accomplished using a variety of techniquesincluding printing, such as screen printing, ink-jet printing, offset-,gravure- or flexographic printing, extrusion-type deposition methods,laser-ablation, electrical erosion, scribing or etching of a continuousconducting layer or by evaporation through a shadow mask (e.g. a maskmade from an array of parallel wires). It should be appreciated thatcontinuous straight lines, as shown, are much easier to pattern than thesmall gate features such as those shown in FIG. 1( a). A characteristicof this gate line pattern may be the substantially constant spacingbetween the stripes which may be defined by e.g. the width of a laserbeam, the size of a scribing stylus, the diameter of a wire (the latterin the case of a shadow mask).

As shown in FIG. 2( b), a continuous first or gate dielectric layer orpattern 102 (e.g. a polymer dielectric insulator such as polyvinylphenol(PVP), poly(vinyl cinnamate), epoxide, polystyrene, PMMA, parylene,polyimide, spin-on-glass, an atomic layer deposited dielectric or aplasma deposited (PECVD) dielectric such as silicon dioxide or siliconnitride, etc.) is formed or deposited using any of a variety of knowntechniques. The dielectric layer may also be an organic-inorganic hybriddielectric, a self assembled monolayer or a stack of self assembledmonolayers such as the self-assembled superlattices (SAS) described byH. C. Lin et al. (Applied Physics Letters 89, 142101, 2006). Polymerdielectrics, for example, may be deposited by spin-coating, spraycoating, extrusion, doctor-blading, dip-coating, evaporation or plasmadeposition. The dielectric layer may also be selectively deposited overonly the gate electrodes. This may be achieved by a selective bindingprocess such as in the case of thiol molecules which selectively bind toa gold surface. The dielectric layer may also comprise multiple layerssuch as an oxide with a self assembled monolayer surface coating or a(polymer) dielectric with a polysilsesquioxane top layer. The functionof the upper layer may be to change the surface energy of the gatedielectric or to smoothen the surface (decrease the surface roughness).In at least one form, this dielectric has a low surface energy whichmeans it is hydrophobic. In one example of a hydrophobic surface, thewater contact angle is above 80 degrees. In other examples, the watercontact angle is above 70 or 90 degrees. A specific example of ahydrophobic dielectric would be a layer of plasma deposited silicondioxide (e.g. 500 nanometers thick) with a hydrophobicoctadecyltrichlorosilane (OTS) self-assembled monolayer coating. Itshould be noted that the gate dielectric layer does not necessarily haveto be deposited, but it may also be grown from the gate metal In oneexample, a gate dielectric is grown on aluminum gate lines by oxidizingthe surface of the aluminum to aluminum oxide in an oxidizing atmospheresuch as ozone. In another example, a layer of tantalum oxide is grown onthe surface of a tantalum gate electrode by anodization. Such surfacesmay also be turned hydrophobic by a silane or silazane treatment, for

Referring now to FIG. 2( c), a pattern 104 (or plurality of features)formed of a second dielectric material is deposited. Of course, thesecond dielectric pattern 104 may be deposited in any of a variety ofmanners. For example, it may be deposited from a solution such as in aprinting method or it may be deposited by evaporation through a shadowmask, or it may be coated (e.g. spin-coated) and patterned usingconventional photolithography. If printing methods are used, a varietyof printing techniques such as inkjet-, offset-, gravure-,flexographic-, aerosol-, screen- or extrusion-printing may be employed.In one embodiment, the pattern 104 may be a jet-printed polymer such asjet-printed PVP (polyvinylphenol), PVA (polyvinylalcohol) or it may be ajet-printed UV-curable (or more generally: radiation curable) polymer.In particular, it may be a printed phase-change material that is printedin a melted (liquid) state and solidifies upon cooling on the printsurface. A wax or UV curable gels are example materials. A phase-changematerial may be also a radiation curable polymer such as a UV-curablepolymer which can be instantly cured by radiation. For example, thephase-change polymer may be an inkjet printable UV curing ink, such asthe HexiJet line of inks from Hexion Speciality Chemicals, Inc. Anotherspecific example are radiation curable phase-change inks described in USPat Appl. 20070142492. In another method, the polymer features aredefined (definition may occur by stamping or microcontact printing) byfirst defining pinning regions for a polymer solution, and then coatingthe polymer so that it is retained only in the pinning regions

This layer or pattern 104 may take a variety of configurations but, inat least one form, defines regions for data lines or areas 106 and pixelpads or areas 108. It also defines a length of a channel 110 for thetransistor region of the device. As can be seen, the vertical alignment(parallel to the gate lines), which usually is very important inconstructing these types of devices, is not a factor in this embodimentusing gate-lines which are shaped as stripes or simple rectangles. Inone embodiment, the pattern 104 (and in particular the data lines 106)is oriented substantially perpendicular to the gate lines 100.

The dielectric or polymer layer or pattern 104 serves to capacitivelydecouple the subsequent conductive traces of the data-layer from thegate-layer. The polymer may be a low-k polymer or it may be relativelythick (e.g., 0.5-5 microns). Particularly, also several layers may beprinted in order to increase the total height. In one form, the polymeris hydrophilic (has a high surface energy). For example, a hydrophilicpolymer used may have a water contact angle of less than 60 deg. Apolymer such as polyvinylalcohol (PVA) or gelatin are examples.

In FIG. 2( d), a conductive material is deposited over the regions ofthe previously deposited polymer, i.e., over the pattern 104. A varietyof techniques may be used. For example, the material may be jet-printed(e.g. printed conducting polymer such as PEDOT:PSS [e.g. Clevios™ fromH. C. Starck of Goslar, Germany], polyaniline, carbon nanotube solutionsor silver nanoparticle solution). In this regard, the printed featuresare aligned to the previously printed polymer pattern. In oneself-aligned deposition method, the polymer (or more generally, thedielectric material) of FIG. 2( c) acts as a fluidic pinning structure.Self-alignment is achieved by selective fluidic pinning on the pattern104. One characteristic of a self-aligned layer 112 may be the almostideal alignment with layer 104 with negligible lateral uneven offsetbetween the structures 112 and 104 (however the structures of layer 112may evenly laterally overhang the structures of layer 104). In thisregard, fluid, such as PEDOT solution or solution of silver, gold,copper or nickel nanoparticles or solution of carbon nanotubes orgraphene, is coated over the surface (e.g. by spin-coating, dip-coatingor by a doctor-blading type method). This solution is only retained inthe areas of the polymer, but it dewets from the surrounding areas. Thiseffect can be achieved by having a hydrophilic (high surface energy)polymer printed on a hydrophobic (low surface energy) gate dielectric.Or, it may be accomplished using structural pinning. For example, if thepatterned polymer surface is rough and the surrounding gate dielectricis smooth, the rough polymer may preferentially pin a liquid. Thepolymer may, therefore, contain micro or nanoparticles that wouldincrease the roughness. Examples of such particles are titanium dioxide,silicon dioxide, zirconium oxide or aluminum oxide particles and alsopolymer particles and the shape of the particles may include wire, tubeand belt shapes such as nanowires, nanotubes or nanobelts. Thoseparticles may be embedded in a polymer such as PVA, for example.Moreover, a thin hydrophobic layer, such as a polysilsesquioxane, may becoated before depositing the conductor. See U.S. application Ser. No.______, filed on even date herewith, entitled, “Method and Structure forEstablishing Contacts in Thin Film Transistor Devices,” naming Daniel etal. as inventors (bearing Attorney Docket No. 20070345-US-NP, XERZ 201958, which is incorporated herein by this reference in its entirety.In the rough regions, the coating will form more pinholes and providemuch better pinning than in the smooth regions. Notwithstanding themanner of deposition of the conductive material, after drying of theovercoated liquid, a patterned conductive layer or pattern 112 forms, asshown in FIG. 2( d). In the case of deposited silver nanoparticles, thelayer typically requires a heating or photonic curing step in order torender the material conductive. It should be noted that the conductivelayer 112 may be also deposited by an electroless plating method if thesurface of the insulating pattern 104 carries a plating catalyst, forexample.

Afterwards, as shown in FIG. 2( e), additional conductive regions may bedeposited to form storage or pixel capacitors 114. These conductivepixel capacitor regions 114 are printed to extend the pixel pads overthe neighboring gate lines. These regions may be printed directly ontothe underlying gate dielectric or they may be formed on a thin pinninglayer. Such a thin pinning layer may comprise another polymer or of athinner version of the dielectric material used to pattern thestructures 104. For example, the layer may be only 10-500 nm thick.Similar dielectric materials as for layer 104 may be used, includingphase-change polymers. Therefore, the regions 114 may also have beenpatterned before the conductive regions 112 have been deposited. Infact, the coating of conductive material shown in FIG. 2( d) may havealso coated the regions 114 at the same time, as will be described inmore detail in FIG. 3( a). Other forms of deposition or formation mayalso be employed. A semiconductor 116 is deposited as well. Thesemiconductor 116 is printed/deposited in the channel region 110. Thesemiconductor may be deposited in many ways, e.g. by jet-printing ofpolymer semiconductor solutions, or precursors (including pentacene,zinc oxide or silicon precursors, as well as carbon nanotubes, siliconnanowires or nanobelts, grapheme, silicon nano particles or othersemiconducting nanoparticles, nanorods, nanoribbons, etc.). Beforedepositing these materials, the surface may be treated with a coatingthat improves the performance of the semiconductor, such as ahydrophobic coating that improves the molecular ordering of an organicsemiconductor. A self-assembled monolayer such as OTS(octadecyltrichlorosilane) or triethyoxyphenylsilane or apolysilsesquioxane are examples. It should be noted that thesemiconductor may also be deposited before depositing the layers 104and/or 112. This would result in a configuration that is a top-contact(staggered) transistor.

FIG. 2( f) shows a cross-section of a TFT structure. The resultingstructure 120 is formed on the substrate 98. The gate lines 100 have thedielectric layer 102 formed thereon. Also shown are the data line region106 and the pixel pad region 108, which serve to define the source anddrain, respectively, for the transistor. The metal conductive layer 112and semiconductor 116 are also shown. It should be appreciated that thedetails of operation of the TFT will be apparent to those of skill inthe art.

FIGS. 3( a) and (b) illustrate that the deposited dielectric layer 106,108 may have various thickness (it is illustrated as a thinner layer inregion 130). For example, polymers with different viscosity may beprinted or varying numbers of layers may be printed in selected regions.The area of the pixel pad which defines the storage capacitor onlydesires a thin polymer layer. For example, a layer as thin as 10-100nanometers or even less would be sufficient to modify the surface andcreate a region that later acts as structure to pin a fluid. The otherareas need a thicker (e.g. 0.5-5 microns) dielectric to reducecapacitive coupling. The exact thickness values depend of course alsovery much on the

So, alternative steps to steps in FIGS. 2( c) and 2(d) above, are usedsuch that, in a region 130 defining the storage capacitor, a thindielectric layer is deposited. In the other regions, a thickerdielectric layer. FIG. 3( b) simply shows that a conductive layer 112may, likewise, be deposited over all such polymer regions. Theconductive layer may be deposited in a self-aligned manner on thedielectric layers 106, 108 (and including region 130) by selectivefluidic pinning.

FIG. 4 illustrates that the gate layer may be patterned slightly morecomplex (e.g., irregularly shaped) than just straight lines in order toprovide a bigger storage capacitor or to reduce capacitive coupling withthe underlying gate line, for example. So, for example, the gate lines100 may have alternating extensions 140 and corresponding notches 142formed therein. This configuration would effectively increase thephysical size of the storage or pixel capacitor by the area of theextension 142. This structure of the gate lines can be described as ameandering shaped separation between neighboring gate lines or as havinga meandering shaped edge. The width of the meander spacing betweenneighboring gate lines would be again substantially constant as it wouldbe defined by the width of a laser beam or the size of a scribing tool,etc. that defines the separation. It should be understood that thesetypes of variations are a function of the design objectives for thecircuit. However, in accordance with the teachings of the presentlydescribed embodiments, in at least one form, the gate line structureshould still be of sufficient width so that precise alignment is lesscritical than for structures that have been heretofore known.

Moreover, the drain or pixel pad area 144 may have a geometry thatreduces capacitive coupling to the gate line. In this regard, the areaof the drain pad may be smaller for multi-layer pixel circuits. Thisgeometry may be particularly suited if a multi-layer pixel structure(with, for example, a mushroom metal layer over another dielectric layerwith via interconnects to area 144) is

FIG. 5 illustrates a further embodiment. Two transistors 150 and 152 maybe connected as part of an electronic circuit, e.g., as an invertercircuit. Here again, the gate feature is wide and the source/draincapacitive coupling to the gate area is reduced by printed dielectriclayers. Using this fabrication method various electronic circuits, suchas shift registers, memory cells, latch circuits, amplifier circuits,etc. may be built. Of course, other configurations may also beimplemented.

in accordance with the presently described embodiments, it should beunderstood that, experimentally, the parasitic capacitance is reduced.For example, by adding a 1 micron polymer layer (having an approximatedielectric constant of 3) over a gate dielectric with a capacitance of14 nF/cm2, the capacitance is reduced to 2.2 nF/cm2.

It should be further understood that experiments evidence that theselective pinning of a polymer conductor (e.g., Baytron HC PEDOT) to anunderlying hydrophilic polymer line is realizable. A solution of VO5polymer (containing ethyl ester of PVM/MA copolymer, aminomethylpropanol, diisopropyl adipate, triethyl citrate, dimethicone copolyol)of Alberto-Culver USA, Inc., Melrose Park, Ill., in polyethylene glycol(PEG) was dispensed in the form of a straight line onto a hydrophobicsubstrate with a fiber by a dip-pen method. After the solvent dried off,a drop of the PEDOT solution was drawn over the surface by means ofanother fiber. The PEDOT solution wetted to the hydrophilic polymerline, but it was repelled by the hydrophobic substrate. The results areconductive lines which are defined by the underlying VO5:PEG polymer(VO5 contains a PVM/MA copolymer, CAS Registry Number 009011-16-9).Here, the hydrophobic surface was a layer of methyl polysilsesquioxane(PSSQ).

The advantages of the presently described embodiments should beapparent. Nonetheless, one advantage is that gate-layer patterning issimple since, in at least one form, only lines or relatively simpledimensionally less critical structures need to be patterned. Thepatterning remains relatively

Another advantage is that less careful alignment between the gate-layerand the source-drain layer is required. Again, even whereirregularly-shaped gate regions are implemented, alignment is a muchsimplified process as compared to heretofore known techniques. Thisresults in a less expensive process.

It should also be understood that variations of the presently describedembodiments are contemplated. For example, the presently describedembodiments are illustrated in an environment and a structure that istypically used in active-matrix backplanes. However, the techniques andstructures of the presently described embodiments apply to individualtransistors or transistor circuits in general. Also, the presentlydescribed embodiments are not limited to an all-printed patterningapproach. Photolithographic patterning approaches may also takeadvantage of these techniques.

It will be appreciated that various of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also thatvarious presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art which are also intended to beencompassed by the following claims.

1. A thin film transistor device comprising: a gate line patterned toextend in a first direction; a first dielectric layer formed over thegate line; a second dielectric pattern deposited on the first dielectriclayer and defining a transistor channel region comprising the gate line;a conductive layer formed on the second dielectric pattern and inalignment with the second dielectric pattern; and, a semiconductorformed in the channel.
 2. The device as set forth in claim 1 wherein thesecond dielectric pattern is oriented on the first dielectric layer in adirection substantially perpendicular to the gate line.
 3. The device asset forth in claim 1 wherein the conductive layer is in alignment withthe second dielectric pattern.
 4. The device as set forth in claim 1wherein the device is part of an active-matrix display backplane.
 5. Thedevice as set forth in claim 1 wherein the device is used in an imagesensor.
 6. The device as set forth in claim 1 wherein the firstdielectric has a low surface energy.
 7. The device as set forth in claim1 wherein the second dielectric is a polymer or a composite of polymerand inorganic particles.
 8. The device as set forth in claim 1 whereinthe second dielectric is printed.
 9. The device as set forth in claim 1wherein the second dielectric has a high surface energy.
 10. The deviceas set forth in claim 9 wherein the conductive layer is aligned on thesecond dielectric by fluidic pinning.
 11. The device as set forth inclaim 1 wherein the device comprises a pixel circuit.
 12. The device asset forth in claim 11 further comprising a pixel capacitor printed overa portion of the gate line and a portion of the pixel pad.
 13. Thedevice as set forth in claim 12 wherein the dielectric in the region ofthe pixel capacitor is thin relative to a thickness of second dielectricfeatures.
 14. The device as set forth in claim 1 wherein thesemiconductor is deposited from a solution.
 15. The device as set forthin claim 1 wherein the semiconductor is jet-printed.
 16. The device asset forth in claim 1 wherein the gate line includes a meandering shapededge.
 17. The device as set forth in claim 1 wherein the device isconnected to at least one second transistor device to form at least oneof an inverter, shift register, memory cell, latch circuit or amplifiercircuit.
 18. A method for forming a thin film transistor, the methodcomprising: patterning a gate line on a substrate in a first direction;depositing a dielectric over the gate line; printing polymer features ina direction perpendicular to the first direction to form a channelcomprising the gate line; forming a conductive layer on the polymerfeatures; and, forming a semiconductor in the channel.
 19. The method asset forth in claim 18 wherein the forming of the conductive layercomprises pinning.
 20. The method as set forth in claim 18 furthercomprising a pixel capacitor to connect a gate line with a selectedportion of the polymer features.
 21. An active-matrix pixel circuitcomprising: an array of gate electrodes formed on a substrate; the gateelectrodes shaped as substantially parallel stripes oriented in a firstdirection; a first dielectric layer formed over the gate electrodes; asecond dielectric layer patterned on the first dielectric layer anddefining transistor channel regions comprising the gate line; aconductive layer formed on the second dielectric layer and in alignmentwith the second dielectric pattern; and, a semiconductor formed in thechannel.
 22. The active-matrix pixel circuit as set forth in claim 21wherein the second dielectric layer comprises a phase-change polymer.23. An active-matrix pixel circuit comprising: an array of gateelectrodes formed on a substrate; the gate electrodes shaped assubstantially parallel stripes oriented in a first direction; a seconddielectric layer of a first thickness patterned on the first dielectriclayer and defining transistor channel regions comprising the gate line;a third dielectric layer of a second thickness patterned on the firstdielectric layer and defining a pixel capacitor region; a conductivelayer formed on the second and third dielectric layer and in alignmentwith the second and third dielectric pattern; and, a semiconductorformed in the channel.
 24. The active-matrix pixel circuit as set forthin claim 23 wherein at least one of the second dielectric layer and thethird dielectric layer comprises a phase-change polymer.
 25. Anactive-matrix pixel circuit comprising: an array of gate electrodesformed on a substrate; the gate electrodes having a meandering shapedseparation with a substantially constant spacing between neighboringgate electrodes; a first dielectric layer formed over the gateelectrodes; a second dielectric layer patterned on the first dielectriclayer and defining transistor channel regions comprising the gate line;a conductive layer formed on the second dielectric layer and inalignment with the second dielectric pattern; and, a semiconductorformed in the channel.
 26. The active-matrix pixel circuit as set forthin claim 25 wherein the second dielectric layer comprises a phase-changepolymer.